Gibson and Francis recently reported that “diastolic left ventricular disease is being increasingly incriminated as a cause of limitation of exercise tolerance, whether or not ejection fraction is normal, though the mechanisms by which it does so are far from clear” and that “it has been suggested that no diastolic abnormality at all need be demonstrated for a diagnosis of possible or probable diastolic heart failure to be made” (“Clinical Assessment of Left Ventricular Diastolic Function,” Heart 2003; 89:231-238).
As noted by Gibson and Francis, left ventricular diastole involves both muscle mechanics and fluid mechanics. Such mechanisms may include decline of the myocardial active state following systole, passive effects of connective tissue (compression or extension of connective tissue may store potential energy from systole and release it in early diastole and, in late diastole, properties of connective tissue may determine ventricular compliance), rapid changes in atrial and ventricular pressures, transmitral flow, interactions from right ventricle and pericardium, and atrial systole. Further, such mechanisms may be interrelated, for example, a fluid pressure may facilitate muscle contraction.
In a clinical setting, a care provider may measure many parameters in an effort to determine whether a patient suffers from diastolic heart failure whereas a typical implantable device lacks resources to perform adequate measurements and make robust determinations. Consequently, a need exists for measurement and determination techniques that can allow an implantable device to diagnose diastolic left ventricular disease.
As described herein, various techniques rely on parameters that relate to muscle mechanics and/or fluid mechanics to detect conditions that may be associated with diastolic heart failure.